public class fi{
    public static void main(String[] args) {
        int n=Integer.parseInt(args[0]);
        int n1=1;
        int n2=1;
        int sum=0;
        if (n<=0){
            System.out.println("参数错误");
            return;

        }
        if (n<=2){
            sum=1;
        }
        else {
            for(int i=3;i<=n;i++){
                sum=n1+n2;
                n1=n2;
                n2=sum;
            }
        }
        System.out.println(sum);
    }
}